The expression of most Staphylococcus aureus virulence factors is controlled by the agr locus, which encodes a two-component signaling pathway whose activating ligand is an agr-encoded autoinducing peptide (AIP). A polymorphism in the amino acid sequence of the AIP and of its corresponding receptor divides S. aureus strains into four major groups. Within a given group, each strain produces a peptide that can activate the agr response in the other member strains, whereas the AIPs belonging to different groups are usually mutually inhibitory. We investigated a possible relationship between agr groups and human S. aureus disease by studying 198 S. aureus strains isolated from 14 asymptomatic carriers, 66 patients with suppurative infection, and 114 patients with acute toxemia. The agr group and the distribution of 24 toxin genes were analyzed by PCR, and the genetic background was determined by means of amplified fragment length polymorphism (AFLP) analysis. The isolates were relatively evenly distributed among the four agr groups, with 61 strains belonging to agr group I, 49 belonging to group II, 43 belonging to group III, and 45 belonging to group IV. Principal coordinate analysis performed on the AFLP distance matrix divided the 198 strains into three main phylogenetic groups, AF1 corresponding to strains of agr group IV, AF2 corresponding to strains of agr groups I and II, and AF3 corresponding to strains of agr group III. This indicated that the agr type was linked to the genetic background. A relationship between genetic background, agr group, and disease type was observed for several toxinmediated diseases: for instance, agr group IV strains were associated with generalized exfoliative syndromes, and phylogenetic group AF1 strains with bullous impetigo. Among the suppurative infections, endocarditis strains mainly belonged to phylogenetic group AF2 and agr groups I and II. While these results do not show a direct role of the agr type in the type of human disease caused by S. aureus, the agr group may reflect an ancient evolutionary division of S. aureus in terms of this species' fundamental biology.

A previously described sequence-based epidemiological typing method for clinical and environmental isolates of Legionella pneumophila serogroup 1 was extended by the investigation of three additional gene targets and modification of one of the previous targets. Excellent typeability, reproducibility, and epidemiological concordance were determined for isolates belonging to both serogroup 1 and the other serogroups investigated. Gene fragments were amplified from genomic DNA, and PCR amplicons were sequenced by using forward and reverse primers. Consensus sequences are entered into an online database, which allows the assignment of individual allele numbers. The resulting sequence-based type or allelic profile comprises a string of the individual allele numbers separated by commas, e.g., 1,4,3,1,1,1, in a predetermined order, i.e., flaA, pilE, asd, mip, mompS, and proA. The index of discrimination (D) obtained with these six loci was calculated following analysis of a panel of 79 unrelated clinical isolates. A D value of >0.94 was obtained, and this value appears to be sufficient for use in the epidemiological investigation of outbreaks caused by L. pneumophila. The D value rose to 0.98 when the results of the analysis were combined with those of monoclonal antibody subgrouping. Sequence-based typing of L. pneumophila is epidemiologically concordant and discriminatory, and the data are easily transportable. This consensus method will assist in the epidemiological investigation of L. pneumophila infections, especially travel-associated cases, by which it will allow a rapid comparison of isolates obtained in more than one country.

Some formerly continent-specific clones have now spread around the world

Deoxyribonucleic acid relatedness studies (S1 nuclease method) showed that 23 unidentified Staphylococcus strains form two homogeneous genomic species related 1 to 9% to 24 type strains representing known Staphylococcus species. These new species were named Staphylococcus lugdunensis and Staphylococcus schleiferi. Strains of S . lugdunensis were susceptible to novobiocin, produced a fibrinogen affinity factor, and failed to produce coagulase, heat-stable nuclease, and staphylokinase. S . lugdunensis strains differed from S. horninis (the phenotypically closest species) by production of ornithine decarboxylase and the fibrinogen affinity factor. The guanine-plus-cytosine content of the deoxyribonucleic acid was 32 mol%. The type strain is N860297 (= ATCC 43809). Strains of S . schleiferi were susceptible to novobiocin, produced a heat-stable nuclease and a fibrinogen aanity factor, and failed to produce coagulase and staphylokinase. S. schleiferi strains differed from S. aureus by production of an antigenically different heat-stable nuclease and the lack of pigmentation, free coagulase, protein A, and Q-ribitol teichoic acid. The guanine-plus-cytosine content of the deoxyribonucleic acid was 37 mol%. The type strain is N850274 (= ATCC 43808).The genus Staphylococcus is currently composed of nonmotile, catalase-positive, facultatively anaerobic, gram-positive cocci. In the last decade, the number of validly published species in the genus Staphylococcus has increased from a few to 24. In clinical practice, Staphylococcus species have been isolated with increasing frequency from infected patients with decreased resistance to infections.When an improved gallery was evaluated for the biochemical identification of staphylococci (l), 47 strains were unidentified although they constituted four biochemical patterns provisionally called NC1, NC2, NC3, and NC4. Subsequently, deoxyribonucleic acid (DNA) relatedness studies identified group NC1 as Staphylococcus haemolyticus and group NC3 as Staphylococcus horninis (unpublished data).The present article reports the delineation of two new genomic species (NC2 and NC4), their phenotypic characterization, and their formal descriptions as Staphylococcus lugdunensis sp. nov. (NC2) and Staphylococcus schle$eri sp. nov. (NC4). MATERIALS AND METHODSBacterial strains. The strains studied were recovered from human clinical specimens and were collected by the French National Reference Center for Staphylococci (Lyon, France) in the last decade. Group NC2 comprised the following 11 strains: 308, 995, 1174, 1257, N850412 (all five from blood), N860165 (intrauterine device), N860172 (thoracic drain), N860210 (umbilicus), N860297 (axillary lymph node), N860314 (abscess drain), and N850420 (unknown specimen). Group NC4 comprised the following 12 strains: N860003, N860207, N860265, N860346, N860375 (all five from blood), N860096, N860097, N860173 (all three from * Corresponding author. wounds), N860215 (urine), N860310 (cranial drain), N850274 Qugular catheter), and N860405 (unknown specimen)....

Current DNA amplification-based typing methods for bacterial pathogens often lack interlaboratory reproducibility. In this international study, DNA sequence-based typing of the Staphylococcus aureus protein A gene (spa, 110 to 422 bp) showed 100% intra-and interlaboratory reproducibility without extensive harmonization of protocols for 30 blind-coded S. aureus DNA samples sent to 10 laboratories. Specialized software for automated sequence analysis ensured a common typing nomenclature.